Protostars and Planets VI, Heidelberg, July 15-20, 2013
The Bouncing Barrier in Protoplanetary Discs: Experimental Studies
Kelling, Thorben (Universität Duisburg-Essen)
Köster, Marc (Universität Duisburg-Essen)
Wurm, Gerhard (Universität Duisburg-Essen)
For dust aggregates in protoplanetary discs a transition between sticking and bouncing in individual collisions at mm to cm size has been observed in the past. This lead to the notion of a bouncing barrier for which growth gets stalled. Here, we present long term laboratory experiments on the outcome of repeated aggregate collisions at the bouncing barrier. About 100 SiO2 dust aggregates of 1 mm in size were observed interacting with each other. Collisions occured within a velocity range from below mm/s up to cm/s. Aggregates continuously interacted with each other over a period of 900 s. During this time more than half a million collisions occured. More than 4000 collisions were analyzed in detail. No temporal stable net growth of larger aggregates was observed even though individual collisions were found to be sticking. Larger ensembles of aggregates sticking together formed but were disassembled again during the further collisional evolution. The concept of a bouncing barrier supports the formation of planetesimals by seeded collisional growth as well as by gravitational instability favouring a significant total mass being limited to certain size ranges. Within our parameter set the experiments confirm that bouncing barriers are one possible and likely evolutionary limit of a self consistent particle growth.
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